Time and again this election season, Mitt Romney has made a basic maneuver: He's attempted to show he will be the Republican presidential nominee by acting like he already is.

Results of early primaries repeatedly proved otherwise, but after three wins on Tuesday and a growing lead in convention delegates, Romney's campaign is aiming at the general election.

Here's NPR's Ari Shapiro.

ARI SHAPIRO, BYLINE: Mitt Romney has always tried to present himself as a general election kind of guy. From the earliest days of the campaign, he talked about President Obama at every turn. Three months ago, Romney mentioned the president less than a minute into his New Hampshire victory speech.

(SOUNDBITE OF SPEECH)

MITT ROMNEY: Today, we're faced with the disappointing record of a failed president.

(SOUNDBITE OF CHEERS AND APPLAUSE)

SHAPIRO: But things didn't go the way the campaign expected. The other Republicans, who Romney always treated as minor bumps in his path to the nomination, became full-fledged roadblocks. Romney had to plunge into the primary mosh pit.

Campaigning in Florida, Newt Gingrich became the first person Romney would talk about.

(SOUNDBITE OF SPEECH)

ROMNEY: He actually resigned after four years in disgrace.

SHAPIRO: Romney and his superPACs spent millions of dollars in state after state to suppress Newt Gingrich, and then Rick Santorum. It wasn't pretty. Everybody's favorability ratings dropped. But it worked. And for the last month or two, Romney has been back in Obama-centric mode on the stump nearly all the time. That can make it hard to discern a shift to general election rhetoric.

Mark McKinnon, who advised President George W. Bush and John McCain, suggests one signpost to look out for.

MARK MCKINNON: I think we'll know when he starts talking about a different kind of immigration plan, when he talks about reaching out to Hispanics in a way that's immigrant friendly.

(SOUNDBITE OF SPEECH)

ROMNEY: Legal immigration is something we conservatives like.

SHAPIRO: This was Romney speaking in Milwaukee this week.

(SOUNDBITE OF SPEECH)

ROMNEY: The immigrant population that comes here doesn't come here for a check. They come here for opportunity. These are our voters.

SHAPIRO: Political scientist Terry Madonna of Franklin and Marshall College in Pennsylvania suggests a different general election indicator.

TERRY MADONNA: It wouldn't surprise me if he now begins to talk about the middle class more - people who have been suffering through the course of this recession.

SHAPIRO: As if on cue, this line popped up in Romney's Wisconsin victory speech Tuesday night.

(SOUNDBITE OF SPEECH)

ROMNEY: A record number of Americans are now living in poverty. And the most vulnerable or the ones that have been hurt the most. Thirty percent of single moms are now living in poverty.

SHAPIRO: And Romney's attacks against President Obama are intensifying, too. He spoke to a gathering of news executives yesterday in Washington, D.C.

(SOUNDBITE OF SPEECH)

ROMNEY: The president came here yesterday and railed against arguments no one is making, and criticized policies no one is proposing. It's one of his favorite strategies: setting up straw men to distract us from his record.

SHAPIRO: So, why pivot now? Well, part of it has to do with the delegate math. It has become nearly impossible for any other Republican to close the gap with Romney. But there's more to it than that, says Professor Madonna.

MADONNA: The president and the Democrats fully understand that Romney is the nominee, and they are beginning to campaign against him. Romney understands that it's in his interest now to avoid talking about his Republican rivals and to focus on the economy and to focus on the president. So, game on.

SHAPIRO: This week, the Democrats dragged Romney into the general election, ready or not. The Obama campaign released its first ad targeting Romney. And President Obama publicly went after Romney by name for the first time on Tuesday, accusing him of supporting a budget that would undermine the middle class.

(SOUNDBITE OF SPEECH)

PRESIDENT BARACK OBAMA: He said that he's very supportive of this new budget, and he even called it marvelous - which is a word you don't often hear when it comes to describing a budget.

SHAPIRO: In the last few election cycles, this shift happened earlier for Republicans. John McCain basically sewed up the nomination in February of 2008. George W. Bush was an early closer, too. So now Romney needs to make up for lost time and money, because as rough as he found it to beat Rick Santorum and the other Republicans, the fight against President Obama will be much harder.